Thesis
A thesis sets forth a proposition that then must be defended. The thesis may state something about the cause or causes of a particular historical event, or about effects or ramifications of historical events. Or it may be about motivating factors within a historical figure -- why someone acted the way they acted in their role in history. A thesis is not simply a statement of a fact that everyone agrees on. A thesis is an arguable claim, and the defense with evidence given for a thesis will want to address counter-claims (any counter-thesis) that someone else might argue.